This invention is in the field of check valves which allow free flow of fluid in one direction and prevent flow in the opposite direction and is particularly suited to area ruled check valves in which the cross sectional area exposed to flow of fluid through its passage through the valve is unchanged so that resistance to flow is minimized.
Check valves are commonly made in the swing check style where a disc or flapper is tilted to allow flow of fluids beneath the flapper in one direction, but the flapper swings shut tightly when flow is reversed. Such a prior art valve is shown schematically in FIG. 1. Because swing check valves often do not close quickly enough, or because the flow pattern through a swing check is not smooth, other styles are sometimes used. The inline check valve shown and described fully in U.S. Pat. No. 4,911,196 is an example of a valve that has superior flow and faster closing characteristics.
An inline or area ruled check valve generally has five principal components. Sometimes these components are made of several pieces, but the combined intent is the same. A body is the main component that holds together all other parts, fits against or between line flanges, and forms the basic conduit through which fluid flows. A piston is mounted within the valve body and is constrained to move only in a lateral direction. The piston moves under urging of the flow away from the seat and fluid flows smoothly through the valve body around the piston and out the downstream end of the valve. When flow is reversed the piston moves under urging of the fluid and also urged by the spring mechanism against the seat and stops all flow. A cage is usually installed to guide the piston in its movement between positions. A seat is usually installed near the upstream end of the valve where the piston will mate easily with it when the flow is reversed. A spring is installed between cage and piston to urge the piston toward the closed or reversed position.
This application is directed only to an inline type of check valve and is particularly directed to a superior method of making such a check valve.